As of this morning, it appears my fears with Garmin Connect have been rectified by Garmin.
By going into reports and clicking Progress Summary...
...it appears all is well again. Relieved.
It may well be that its down to a browser compatibility issue. My work machine uses Internet Explorer. I did have a few issues using Firefox in March and early April in the run up to the introduction of the new interface, so will put it down to that.
I'll have a proper play with Connect later but I'm a happy man again as I like to see the numbers (can you tell I'm an accountant?!?!)